<!DOCTYPE html>
 
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <meta http-equiv="X-UA-Compatible" content="ie-edge">
  <title>Document</title>
  <style>
    .continer {
      height: 100px;
      width: 100px;
      background-color: aqua;
    }
 
    .continer div {
      display: none;      /*默认隐藏*/
    }
 
    .continer:hover div {
      display: initial;      /*当鼠标hover时展示*/
    }
  </style>
</head>
 
<body>
  <div class="continer">
    文字内容文字内容
    <div>我是鼠标悬停展示的内容</div>
  </div>
</body>